Tow control for gliders



April 1945. w. L. EFFINGER. 'JR

' TOW CONTROL FOR GLIDERS Filed May 11, 1943 IN V EN TOR. Wu. 1. /AM Lou/.5 f'firmikdn.

& BY

Patented Apr. 10, 1945' 'r l t i (l L OFFICE mow common EQR GLIDERS william LouisEl'finger, J r., WestHempstead, N. -Application-:May .11, 1943, Serial No.-486 ;494

7 Claims. emo s) FII'hB JJPIBSBHt'PiHVEILtiOII relates to the -control of towed gliders toukeepthe glider on its course autoerratically without theneed of manual control. :The invention is thus particular1y wapplicable vfor "ruse whereua-[gliderfis fiown-withoutta pilot-as for example, a model glider. t

A glider array-he rtO'WBd continuously, for example, hy a power planedoriit may be :launched by a tow slin'eiand .then allowed to-soar: freely 'unti'l it iands. In the slatter -.case; the :sglider i-is towed until qiti'attains :sufiicientt altitude, whereupon the pull on athetowiine discontinued, andthe tow line -.is prefembl5 released fromnthe glider-vso-zras motto impede its; flight. in the: presentappliew tion the inventlon'is shown byway (of example em bodied in a glider intended for tow line launchin gbututhe towinsran obviouslybecontinued-as longesdesired. Y

*sItisanobioct the-present invention-to rovide an -automatic: 09111315011101 keeping azgllderzon it its eourse-while itiis being-towed. In-accordance withathe: ,iIEWBIIfiOIITtmS :is accomplished by pro- Yidingtthe gglider :with movable eontrolisuriaces which are operated automatically by the :direction of pull ;on "the :towline w-tozwsteer the iglider.

:axis provided rby'ihinge-pins -16.

rhasi-a body-"structure comprising a fuselage '5',

Wings ll, horizontal:stabilizers"I12wand "vertical def-the glider. .IIn theremb'odim'ent illustrated the' drawing, 13193001113101 :surfaces are provided .inttheyform of a-rudder l 4; and:aztrim tan-l5. 'Ihe rudder is swingahle :about-a vertically extending The trim tab v-is zshown' mnsedito the rudder "by means of hin es .ll-lpreferahlyriormed of pieces of-isheet meta1-securedtoa'both" therzrudder .and dine-trim tab' so that theposition of theitrim tab can-be addusted lay;- bending the metal 'hinges, .Wherenptm the tabs will heheldzin adjnstedmosition.

rlnylaccordance "with --:the present invention the position of movable surfaces controlling the .direction-rof flight 'of .the glider during "'towing is automatically controllediby the-'directionofzpull of the tow line. The'automatlc: control ;is achieved by means f ,;a control element 'responsiveto changes indirection of pull of the 'tow' line ::and connected with control surfaces to :ohange wrthe position.oftsaidzsurfacesznponchange direction and simpleconstruction reliable mite-operation and of such light weight that it 11085 not substanmtinventicmwithsportions:efithe:bodystructure broken T BfWMitO ishowzrthmcontrol mechanism.

.;EE'lI.;1 2-?is =18. 'odew: :taken approximately en the linez zlinfifigfll.

ifig..if3 isean-senlargedattagmentary horizontal sentionalwiewitaken-zonithehamerline as inEig. 2..

Fig. 4 is asmall sealesdiagrammaticview illustrating the operation :ofxthe :oontrol .mechanism iniaccordancewith mydnvention.

an tnemawinaatne-iinvention showncem bodied inmowimeosunenemnm. manner:

of the tow line pull. Inthe form-.shownzby way of example in the drawing, the a control "element comprises -.a vertically extending shaft .18 rotatably. supported inuth'e g-liderstructure by bearing is and zlllandmavingiat its lower end'an arm :2l which projects forwardlyifrom said shaft and is provided :atits forward-end with :meansior releasably attaching "a tow line. Forexample the forwardgendzofitheerm is bent toformaa rearwardly and \downwardlyvopening :hook :22 over which "at loo 23' of; the tow line -24 ,may he 1 slipped. The arm-2 Land hook 22-,are locatedtbelow thef uselage so ithat the'tow 111118 can jbB readily attached and detached. The shaft I8 is also provided with anrarm: 215 whichmrolficts laterally fromthe shaft and shownpat-an angle of approximately 45 to the longitudinalaxisof the glider. The arm 25:15 conneetediby ailink26.;with an arm ZT-pro- .iectinglaterallyfrom the-rudder l4. It will be seen that the 2arm -25\.of the controlielement and thetarm :2 :of thezrudder rolecttoward opposite sides FOf glider-:anidwthat the link *26 crosses over fromaone-zeide to the: other. -Hence if the control element-is eturned ,vinya counterclockwise direction as-viewed Fig.-

.labout-the vertically extendin waxisdetermined by the hearings l9 anddfl; theiiiinls 5-26 -willqbe'moved, forwardly and the-:ruddernwlllbe swing in r a clockwise direction aboutzthe vertically extending: axisxdetermined aby hinge-pins l 6. v-flonvereeltti if itheicontrolelement is turned inta elochwise idireotiontherudder will be swung about its hinge pins in a counterclockwise direction. It will be understood that in referring to the axes of the control element and the rudder as being vertically extending, and hence approximately parallel to one another, it is meant that they extend in a generally up and down direction and need not be perpendicular to the longitudinal axis .of the glider or to the horizontal plane passing through the longitudinal axis. The axis about which the rudder swings is frequently inclined, and the axis of the control element may also be inclined, if desired. The control element can conveniently be made of a single piece of wire or rod bent to provide the forwardly projecting arm 2|, the hook 22 and the laterally projecting arm 25 including a pivot pin 28 for pivotally connecting the glider arm with the link 26.

The control element is preferably held in a prethe left and hence turn the slider to the right. As the plane turns toward the direction of pull of the tow line, the sidewise pull on the arm 2| of the control element is progressively decreased and the control element will be restored to its neutral position as soon as the glider is "again headed in the direction of pull of the tow line. It will thus be seen that the amount the rudder is swung by the control element depends on the direction of pull of the tow line. If the direction aof pull on the tow lineis toward the left side of the glider, the rudder will likewise be swung toward the left, as shown by dotted lines in Fig.

determined position by a resilient element 30 for example an elastic band or a spring attached at one end to the arm 25. The other end of the spring is anchored to the body structure and the anchoring point may, if desired, be made movable oradjustable in order to vary the position in which the control element is held. The resilient element may be attached in other ways to hold the control element in predetermined position. For example, a resilient element maybe attached to another arm provided on the control element or opposed resilient elements acting in opposite directions may .be attached to arm or other arms with which theresilient element is provided. By reason of the link 28 connecting the rudder with the control element, the rudder is likewise held in predetermined position by the resilient element 30. It will be seen that the resilient element opposes movement of the control member from neutral position and tends to return it to said position if it has been displaced. If desired, suitable damping means, for example, a dash pot may be provided to prevent oscillation of the control element. However, this is not ordinarily necessary, particularly if the resilient element is in the form of an elastic band having a certain amount of internal friction. 1

In flying the glider shown by way of example in the drawing, the tow line attached to the hook 22 of the forwardly projecting arm 2| of the control element and the other end of the line is pulled by the moving .object by which the glider is to be towed.- For tow line launching, the point of attachment of the tow line to the control element and hence to the glider is preferably below andforward-of the center of gravity of the glider and, as will be apparent from Fig. 1', well be-' low the center oflift and center of resistance of the glider so that a pull on the tow line creates a couple causing the glider to be inclined upwardly at a proper angle of attack for climbing.

vAs long as the pull on the tow line is straight about its axis. Thus, if the pull of the tow line is toward the right, as shown in solid lines in Fig. 4. the control element will be swung in a clockwise direction and the rudder will be swung in a counterclockwise direction more toward the right. This will swing thetail of the glider to 4 andthe glider will by reason of the left rudder turn to the left until its deviation from the course determined by the direction of pull on the tow line has been corrected. It will be understood that when the glider is above the towing object, as occurs for example in launching a glider by towing it from the ground, the tow line will pull downwardly a well as forwardly as illustrated in Fig. 1. In this case the direction of-flight of the glider is determined by the horizontal component of the pull of the tow line,'i. e., a component perpendicular to the pivotal axis of the control element.

The resilient element 30 opposes movement of the control element by a sidewise pull from the tow'line, and thereby keeps the control element from being swung as far as it would otherwise. This resilient damping of the action of the control element prevents any overcontrol, i. e},an y tendency to over correct the deviation'from the prescribed course and swing first to one sided the course and then to 'the other in a 'z ig zag fashion. I v

When sufficient altitude has been attained in tow line launching, the pull on thetow line is released, and the tow line drops off the hook 22.

40 After the tow line has been released from 'the control element, the controlelement and rudder are held in neutral'position by the resilient element 30. Ordinarily, this predetermined position will be with the rudder in line with or parallel to the longitudinal axis of the glider. If it is desired for the glider to fly in a circle after being released, the trim tabgli is adjusted to one side'or the otherbefore launching the glider to obtain the circular course desired. Alternatively, by changing the positionof attachment of the resilient element 30 it can be made to hold the rudder in any desired position when there isno pull on the tow line. Thus by adjusting the control element or'by means of other controls'urfaces such as the trim tab' IS, the glider can be made to fly' along a course off-set from the course of the towing object. While in the embodiment shown in the drawing the control element responsive to the pull of the tow line controls a singlerudder, it will'be understoodthat the invention is equally applicable to twin tail gliders "and to the controlof other vertical or horizontal control surfaces,"for example, movable surfaces used in steering a flying wing type of glider. In'refe'rring. to vertical and horizontal with reference to the 'glider'in the specification and theac'companyingclairns. it will be understood that the reference is tdvertical and horizontal direction when the glider'is in a level position and will accordingly vary'with variations in the position of the glider. 1

While the control mechanism in accordance with my invention is extremely simple in' con struction,it has beenfound to be effective and reliable in operation. During towing the glider is kept on its course by the automatic manipulation of the rudder, by the control element responsive to the direction of pull of the tow line. When the tow line is released-control of the glider may, if desired, be taken-over by any other control provided. For example, the course may be controlled manually or by a predetermined setting of auxiliary control surfaces such as trim tabs. Alternatively, the direction of flight, of the glider after release of the tow line may be determined by the position in which the rudder is held by the resilient element acting on the control mechanism.

What I claim and desire to secure by Letters Patent is:

1. In a glider towed by a towline, the combination of a rudder swingable about a vertically extending axis, a control element adapted to be releasably connected with the towline at a point below the center of gravity of the glider and swingable about a vertically extending axis by changes in the direction of pull of said towline, and connections between the control element and r the rudder to swing the rudder in a clockwise direction when the control element is swung counterclockwise, and to swin the rudder in a counterclockwise direction when the control element is swung clockwise.

2. In a towline launched glider having a body structure and a rudderfor controlling the direction of flight of the glider, a control element pivotally supported by said body structure for tically extending axis, means for releasably attaching a towline to said element at a point forwardly of said axis and below the center of resistance of the glider in such manner that a pull on the tow line creates a couple causing the glider to be inclined upwardly at a proper angle of attack for climbing, said control element being responsive to' the horizontal component'of the direction of pull of the towline, a rudder for controlling the direction of flight of the glider, and

connections between the rudder and said control 4 element to change the position of the rudder by a change in the direction of pull of the towline.

4. In atowline launched glider, the combination of a control element swingable about a vertically extending axis, means for releasably attaching a towline to said element at a point forwardly of said axis and below the center of resistance of the glider in such manner that a pull on the towline tends to increase the angle of attack of the glider and to swing said control element about its axis in accordance with the direction of said pull, a rudder for controlling the direction of flight of the glider, connections between the rudder and said control element for changing the position of the rudder upon change in the direction of pull of the towline, and means for dampening said changes in rudder position.

5. In a towline launched glider, the combination of a movable control surface for controlling the direction of flight of the glider, a movable control element for controlling the position of said surface, means for resiliently holding said control element and control surface in a predetermined position to steer the glider when in free flight, and connections between said control element and towline to control the direction of flight of the glider by changing the position of said control surface in accordance with the direction of pull of said towline when the glider is being towed, said towline being attached to said control element at a point below the center of lift of the glider in such manner that a pull on the towline creates a couple causing the glider to be inclined at the desired angle of attack. 6. In a towline launched glider, the combination of a rudder, means forresiliently holding said rudder in a neutral position, an adjustable trim tab for directing the glider on a predetermined course when said glider is in free flight with the rudder held in neutral position, and a control element responsive to the direction of pull of a towline and connected with said rudder to change the position of the rudder upon a change in direction of said pull while the glider is being towed, said towline being attached to said control element at a point below the center of lift of the glider in such manner that a pull on the towline creates a couple causing the glider to be inclined at the desired angle of attack.

7. In a towline launched glider, the combination of a control element responsive to the direction of pull of the towline and having an angularly movable portion, a control surface for controlling the direction of flight of the glider, connections between said control surface and said control element whereby said surface is movable by the control element upon change in the direction of pull of the towline, and means for resiliently holding said control surface in predetermined position and for dampening movementof said surface from said position by the control element, said resilient and dampening means comprising a resilient tension element acting on said angularly movable portion of said control 'element and in line therewith when in neutral position.

WILLIAM LOUIS EFFINGER, JR. 

